1. Field of the Invention
The present invention relates to an automatic coffee machine, in which the ground coffee is delivered to an infusion chamber, in which it is compressed between an infuser piston and a filter piston and from which exits a coffee beverage, deliverable as coffee alone or, combined with milk, in the form of cappuccino. A toroid-shaped rubber ring is positioned to stabilize the seal between the infusion chamber and the infuser piston while the infuser piston is working in the infusion chamber to perform a compression of the ground coffee.
2. The Prior Art
In known machines of this kind, the infuser piston has, in a fixed position, a toroid rubber ring (a so-called O-Ring) for the seal. This ring is subject to considerable wear, due to the entry stress of the infuser piston into the infusion chamber and the scraping action generated along the entire path of the infuser piston movement.